#region Copyright ?2001-2003 Jean-Claude Manoli [jc@manoli.net]
/*
 * This software is provided 'as-is', without any express or implied warranty.
 * In no event will the author(s) be held liable for any damages arising from
 * the use of this software.
 * 
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 * 
 *   1. The origin of this software must not be misrepresented; you must not
 *      claim that you wrote the original software. If you use this software
 *      in a product, an acknowledgment in the product documentation would be
 *      appreciated but is not required.
 * 
 *   2. Altered source versions must be plainly marked as such, and must not
 *      be misrepresented as being the original software.
 * 
 *   3. This notice may not be removed or altered from any source distribution.
 */ 
#endregion

using System;
using System.IO;
using System.Reflection;
using System.Text;
using System.Text.RegularExpressions;

namespace Forest.Core.Html.CodeFormatter
{
	/// <summary>
	///	Provides a base implementation for all code formatters.
	/// </summary>
	/// <remarks>
	/// <para>
	/// To display the formatted code on your web site, the web page must 
	/// refer to a stylesheet that defines the formatting for the different 
	/// CSS classes generated by CSharpFormat:
	/// .csharpcode, pre, .rem, .kwrd, .str, .op, .preproc, .alt, .lnum.
	/// </para>
	/// <para>
	/// Note that if you have multi-line comments in your source code
	/// (like /* ... */), the "line numbers" or "alternate line background" 
	/// options will generate code that is not strictly HTML 4.01 compliant. 
	/// The code will still look good with IE5+ or Mozilla 0.8+. 
	/// </para>
	/// </remarks>
    public abstract partial class SourceFormat
	{
		/// <summary/>
		protected SourceFormat()
		{
			_tabSpaces = 4;
			_lineNumbers = false;
			_alternate = false;
			_embedStyleSheet = false;
		}

		private byte _tabSpaces;

		/// <summary>
		/// Gets or sets the tabs width.
		/// </summary>
		/// <value>The number of space characters to substitute for tab 
		/// characters. The default is <b>4</b>, unless overridden is a 
		/// derived class.</value>
		public byte TabSpaces
		{
			get { return _tabSpaces; }
			set { _tabSpaces = value; }
		}

		private bool _lineNumbers;

		/// <summary>
		/// Enables or disables line numbers in output.
		/// </summary>
		/// <value>When <b>true</b>, line numbers are generated. 
		/// The default is <b>false</b>.</value>
		public bool LineNumbers
		{
			get { return _lineNumbers; }
			set { _lineNumbers = value; }
		}

		private bool _alternate;

		/// <summary>
		/// Enables or disables alternating line background.
		/// </summary>
		/// <value>When <b>true</b>, lines background is alternated. 
		/// The default is <b>false</b>.</value>
		public bool Alternate
		{
			get { return _alternate; }
			set { _alternate = value; }
		}

		private bool _embedStyleSheet;

		/// <summary>
		/// Enables or disables the embedded CSS style sheet.
		/// </summary>
		/// <value>When <b>true</b>, the CSS &lt;style&gt; element is included 
		/// in the HTML output. The default is <b>false</b>.</value>
		public bool EmbedStyleSheet
		{
			get { return _embedStyleSheet; }
			set { _embedStyleSheet = value; }
		}

		/// <overloads>Transform source code to HTML 4.01.</overloads>
		/// 
		/// <summary>
		/// Transforms a source code stream to HTML 4.01.
		/// </summary>
		/// <param name="source">Source code stream.</param>
		/// <returns>A string containing the HTML formatted code.</returns>
		public string FormatCode(Stream source)
		{
            var reader = new StreamReader(source);
			string s = reader.ReadToEnd();
			reader.Close();
			return FormatCode(s, _lineNumbers, _alternate, _embedStyleSheet, false);
		}

		/// <summary>
		/// Transforms a source code string to HTML 4.01.
		/// </summary>
		/// <returns>A string containing the HTML formatted code.</returns>
		public string FormatCode(string source)
		{
			return FormatCode(source, _lineNumbers, _alternate, _embedStyleSheet, false);
		}

		/// <summary>
		/// Allows formatting a part of the code in a different language,
		/// for example a JavaScript block inside an HTML file.
		/// </summary>
		public string FormatSubCode(string source)
		{
			return FormatCode(source, false, false, false, true);
		}

		/// <summary>
		/// Gets the CSS stylesheet as a stream.
		/// </summary>
		/// <returns>A text <see cref="Stream"/> of the CSS definitions.</returns>
		public static Stream GetCssStream()
		{
			return Assembly.GetExecutingAssembly().GetManifestResourceStream(
				"Manoli.Utils.CSharpFormat.csharp.css");
		}

		/// <summary>
		/// Gets the CSS stylesheet as a string.
		/// </summary>
		/// <returns>A string containing the CSS definitions.</returns>
		public static string GetCssString()
		{
            var reader = new StreamReader(GetCssStream());
			return reader.ReadToEnd();
		}

		private Regex codeRegex;

		/// <summary>
		/// The regular expression used to capture language tokens.
		/// </summary>
		protected Regex CodeRegex
		{
			get { return codeRegex; }
			set { codeRegex = value; }
		}

		/// <summary>
		/// Called to evaluate the HTML fragment corresponding to each 
		/// matching token in the code.
		/// </summary>
		/// <param name="match">The <see cref="Match"/> resulting from a 
		/// single regular expression match.</param>
		/// <returns>A string containing the HTML code fragment.</returns>
		protected abstract string MatchEval(Match match);

		//does the formatting job
		private string FormatCode(string source, bool lineNumbers, 
			bool alternate, bool embedStyleSheet, bool subCode)
		{
			//replace special characters
            var sb = new StringBuilder(source);

			if(!subCode)
			{
				sb.Replace("&", "&amp;");
				sb.Replace("<", "&lt;");
				sb.Replace(">", "&gt;");
				sb.Replace("\t", string.Empty.PadRight(_tabSpaces));
			}
			
			//color the code
			source = codeRegex.Replace(sb.ToString(), new MatchEvaluator(this.MatchEval));

			sb = new StringBuilder();
			
			if (embedStyleSheet)
			{
				sb.Append("<style type=\"text/css\">\n");
				sb.Append(GetCssString());
				sb.Append("</style>\n");
			}

			if (lineNumbers || alternate) //we have to process the code line by line
			{
				if(!subCode)
					sb.Append("<div class=\"csharpcode\">\n");
                var reader = new StringReader(source);
				int i = 0;
				string spaces = "    ";
				string line;
				while ((line = reader.ReadLine()) != null)
				{
					i++;
					if (alternate && ((i % 2) == 1))
					{
						sb.Append("<pre class=\"alt\">");
					}
					else
					{
						sb.Append("<pre>");
					}

					if(lineNumbers)
					{
						var order = (int)Math.Log10(i);
						sb.Append("<span class=\"lnum\">" 
							+ spaces.Substring(0, 3 - order) + i.ToString() 
							+ ":  </span>");
					}
					
					if(line.Length == 0)
						sb.Append("&nbsp;");
					else
						sb.Append(line);
					sb.Append("</pre>\n");
				}
				reader.Close();
				if(!subCode)
					sb.Append("</div>");
			}
			else
			{
				//have to use a <pre> because IE below ver 6 does not understand 
				//the "white-space: pre" CSS value
				if(!subCode)
					sb.Append("<pre class=\"csharpcode\">\n");
				sb.Append(source);
				if(!subCode)
					sb.Append("</pre>");
			}
			
			return sb.ToString();
		}

	}
}
